You should at least cheat right: mean( replicate( 10^5, t.test(rnorm(10, .1), a='g')$p. < .05))
;-) @Greg : neat! On Thu, May 6, 2010 at 10:54 PM, David Winsemius <dwinsem...@comcast.net>wrote: > > On May 6, 2010, at 3:51 PM, Greg Snow wrote: > > Golf entry: >> >> mean( replicate( 10000, t.test(rnorm(10, 0.1, 1), alternative='greater', >> mu=0, conf.level=0.95)$p.value < 0.05)) >> >> Or >> >> mean( replicate( 10000, t.test(rnorm(10, .1), a='g')$p.value < .05)) >> >> or even >> >> mean( replicate( 10000, t.test(rnorm(10, .1), a='g')$p. < .05)) >> > > Having failed with my efforts with: > summary(lm(rnorm(10,.1)~1))[[4]][4] < .05 .... > > I'm going to cheat: > mean( replicate( 10^3, t.test(rnorm(10, .1), a='g')$p. < .05)) > > -- > David > > > >> -- >> Gregory (Greg) L. Snow Ph.D. >> Statistical Data Center >> Intermountain Healthcare >> greg.s...@imail.org >> 801.408.8111 >> >> >> -----Original Message----- >>> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- >>> project.org] On Behalf Of Joris Meys >>> Sent: Thursday, May 06, 2010 9:57 AM >>> To: Dimitri Liakhovitski >>> Cc: r-help@r-project.org; level >>> Subject: Re: [R] T-test & for loop >>> >>> Hehe, >>> >>> those homeworks. If you can explain this code to the professor, you >>> surely >>> passed. >>> >>> n <-10000 >>> obs.rej.rate <- sum(sapply(1:n,function(x){t.test(rnorm(10, 0.1, >>> 1),alternative="greater",mu=0,conf.level=0.95)$p.value <0.05}))/n >>> obs.rej.rate >>> >>> This could actually be another round of R-golf. Anybody up to it? >>> >>> >>> >>> On Thu, May 6, 2010 at 3:03 AM, Dimitri Liakhovitski >>> <ld7...@gmail.com>wrote: >>> >>> Sounds like homework (you are not supposed to post homework-related >>>> questions here - read the guidelines). But anyway: >>>> >>>> nr.of.rejections=0 >>>> for(i in 1:10000){ >>>> x=rnorm(10, 0.1, 1) >>>> result<- >>>> >>> t.test(x,alternative="greater",mu=0,conf.level=0.95)$p.value >>> >>>> if(result<0.05) nr.of.rejections = nr.of.rejections+1 >>>> } >>>> print(paste("Observed number of rejections of Ho:", nr.of.rejections, >>>> >>> sep=" >>> >>>> ")) >>>> observed.rejection.rate = nr.of.rejections/10000 >>>> print(paste("Actual rejection rate of Ho:", observed.rejection.rate, >>>> >>> sep=" >>> >>>> ")) >>>> >>>> However, it's not Type 1 error rate. It's the observed rejection >>>> >>> rate. Type >>> >>>> 1 error is probability of rejecting Ho when it is actually TRUE. And >>>> >>> in >>> >>>> your >>>> case (x = rnorm(10,0.1,1) your null hypothesis (that mean = 0) is NOT >>>> >>> true >>> >>>> because,as you know, in the population the mean is 0.1. >>>> >>>> Dimitri >>>> >>>> >>>> On Wed, May 5, 2010 at 2:31 PM, level <lev_lamb...@hotmail.co.uk> >>>> >>> wrote: >>> >>>> >>>> >>>>> I have been set a question which i understand statistically but my >>>>> inability >>>>> with R is preventing me from finishing it.. >>>>> >>>>> My question is that we to calculate the frequency of Type 1 errors >>>>> >>>>> starting with x = rnorm(10, 0.1, 1) >>>>> >>>>> then doing a t-test seeing whether you reject the null hypothesis >>>>> >>>> (Ho >>> >>>> mu >>>> >>>>> = >>>>> 0) alternative is mu > 0 >>>>> >>>>> Then i am supposed to use a for loop to do this procedure 10 000 >>>>> >>>> times >>> >>>> keeping track whether the null has been rejected or not. If anyone >>>>> >>>> can >>> >>>> help >>>>> with me it would be great help >>>>> >>>>> cheers >>>>> >>>>> -- >>>>> View this message in context: >>>>> http://r.789695.n4.nabble.com/T-test-for-loop- >>>>> >>>> tp2131458p2131458.html >>> >>>> Sent from the R help mailing list archive at Nabble.com. >>>>> >>>>> ______________________________________________ >>>>> R-help@r-project.org mailing list >>>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>>> PLEASE do read the posting guide >>>>> http://www.R-project.org/posting-guide.html >>>>> and provide commented, minimal, self-contained, reproducible code. >>>>> >>>>> >>>> >>>> >>>> -- >>>> Dimitri Liakhovitski >>>> Ninah.com >>>> dimitri.liakhovit...@ninah.com >>>> >>>> [[alternative HTML version deleted]] >>>> >>>> ______________________________________________ >>>> R-help@r-project.org mailing list >>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>> PLEASE do read the posting guide >>>> http://www.R-project.org/posting-guide.html >>>> and provide commented, minimal, self-contained, reproducible code. >>>> >>>> >>> >>> >>> -- >>> Joris Meys >>> Statistical Consultant >>> >>> Ghent University >>> Faculty of Bioscience Engineering >>> Department of Applied mathematics, biometrics and process control >>> >>> Coupure Links 653 >>> B-9000 Gent >>> >>> tel : +32 9 264 59 87 >>> joris.m...@ugent.be >>> ------------------------------- >>> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-help >>> PLEASE do read the posting guide http://www.R-project.org/posting- >>> guide.html >>> and provide commented, minimal, self-contained, reproducible code. >>> >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > David Winsemius, MD > West Hartford, CT > > -- Joris Meys Statistical Consultant Ghent University Faculty of Bioscience Engineering Department of Applied mathematics, biometrics and process control Coupure Links 653 B-9000 Gent tel : +32 9 264 59 87 joris.m...@ugent.be ------------------------------- Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
